﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace HomeWork
{
    class Demo1
    {
        public static void Round(){
            const double PI = 3.14;
            double r = 0;

            Console.WriteLine("请输入圆的半径：");
            string v = Console.ReadLine();
            r = double.Parse(v);

            Console.WriteLine("圆的面积为：" + PI * r * r);

            Console.ReadLine();
        }
    }
}
